First let me start off by mentioning I am no Ruby expert. I have installed quite a few custom applications on my WestHost account, so if the below instructions do not work for you, post a reply with the error that you received so we can see if you are missing something I may have previously installed.

First off make sure the GCC is installed through your Site Manager by going to "Install and Manage" under Site Applications. The GCC is located under the development section.

After the GCC is compiled, visit

http://www.ruby-lang.org/en/downloads/

That should take you to the Ruby download page. From here you can select which one you'd like to download. For this tutorial (if you could call it that) I will be using the latest tar.gz version.

I simply copied the location of the link which in this case was,

ftp://ftp.ruby-lang.org//pub/ruby/ru...-stable.tar.gz

After you have this you are ready to SSH into your account utilizing your favorite terminal application.

Once SSH'd in, I ran the following commands,

Code:
wget ftp://ftp.ruby-lang.org//pub/ruby/ruby-1.9-stable.tar.gz
This should download the .tar.gz file to wherever you currently are in your VPS. Your current location should not matter for the rest of the installation.

Once you have the tar.gz file, we need to unpack it with the following command,

Code:
tar xvzf ruby-1.9-stable.tar.gz
This should create a folder wherever you are named ruby-1.9* as it is the -stable release it will name it whatever the current/latest version is, in my case it was 1.91-p243, note this may be different depending on how long it has been since this was written.

Now lets navigate into the folder with,

Code:
cd ruby-1.9.1-p243/
Once inside, we are going to configure the installation to install into a folder we have permission to install to, in this case /usr/local/ruby1.9/. You are more than welcome to choose just /usr/local/ruby/ I did not because some users will already have ruby installed and I did not want to have it interfere.

Code:
./configure --prefix=/usr/local/ruby1.9/
Once the configure finishes, we need to run the make command,

Code:
make
This will take a substantial amount of time, and should hopefully finish with no errors. Once it finishes we need to run make install to finish the installation.

Code:
make install
Once the make install is finished, Ruby should now be installed in /usr/local/ruby1.9/

One other thing to note, in order to run Ruby from any location we need to add the ruby bin file to /usr/bin/. If an older version of Ruby is present, there is most likely already a symbolic link in /usr/bin. You will want to first navigate to /usr/bin and make sure there is not a symbolic link named ruby. If there is remove it with,

Code:
rm /usr/bin/ruby
If it does not exist, simply create a new symbolic link with the following command,

Code:
ln -s /usr/local/ruby1.9/bin/ruby /usr/bin/ruby
Now you should be able to execute Ruby commands from any location within the VPS. As I am no Ruby expert, to test the installation I just ran the command,

Code:
ruby --version
And received the output,

Code:
ruby 1.9.1p243 (2009-07-16 revision 24175) [i686-linux]
Which leads me to believe it was successfully installed. If after following this tutorial you run into any issues running or utilizing Ruby, just reply to the post and I'll take a look at my test installation. Keep in mind, I am no Ruby expert however so my support may be limited.

I hope this helps those in need of a newer version of Ruby on their VPS.